JP2013221974A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus in which, in a process cartridge after being detached because of decrease in developer amount, improvement of electrification characteristic of toner carried on a developer carrier in a developing unit and stability of a coating state are achieved so as to obtain a more stable image.SOLUTION: An image forming apparatus 100 is configured to include: an electrode 17 for detecting the amount of toner T in a cartridge 10 having a developing unit; and a controller 50 for controlling so that, when the cartridge 10 is mounted to an apparatus body 100A, the electrode 17 detects the amount of the toner T in the cartridge 10 and when the cartridge 10 is dismounted after it is determined that the amount of the toner T in the cartridge 10 is decreased on the basis of a result of the detection by the electrode 17, a process condition for the inside of the apparatus body 100A is changed depending on whether it is a used cartridge 10 having been already used or another use cartridge to be mounted separately.

Description

  The present invention relates to an image forming apparatus that employs an electrophotographic system.

  Conventionally, inventions described in Patent Document 1 and Patent Document 2 relating to an image forming apparatus in which a cartridge having a developing device is detachable are known. In the invention described in Patent Document 1, a toner to which particles having a polarity opposite to that of the toner are externally added is used. When the toner remaining amount detecting means detects that the toner remaining amount is equal to or less than the predetermined amount, the charging and developing bias is applied so that the toner charged to the opposite polarity to the desired polarity is discharged from the developer container during non-image formation. Change the setting. According to such a configuration, reversal fog that increases just before the toner runs out is suppressed, and a good output image can be obtained from the initial stage over a long period of time.

  The invention described in Patent Document 2 is an invention relating to an image forming apparatus that displays on a display unit such that a cartridge is shaken when it is determined that “toner has run out” based on a detection result of a remaining amount detection sensor. When the cartridge is mounted again and the remaining amount of toner is detected and it is determined again that “toner has run out”, a display prompting replacement of the cartridge is displayed.

  In addition, when detecting the remaining amount of toner, before the toner is completely lost and the image that the user wants to output becomes defective, a message such as “low toner amount” or “no toner amount” is given to the user. Are often displayed. In other words, even when “no toner remaining” is displayed, the toner is not completely exhausted.

  When “no toner remaining” is displayed, the toner inside the cartridge is roughly divided into two, and there are toner near the developing roller and toner adhering to the inner wall of the developing container. When the cartridge is replaced, these two toners are used without being used.

  The toner in the vicinity of the developing roller is affected by the history of the output image, etc., and a portion that is carried more or less is formed on the surface of the developing roller. There is a possibility that the uniformity in the longitudinal direction will be impaired. On the other hand, the toner remaining on the inner wall of the developing container without moving is hardly subjected to the charging history by the regulating member.

  When the cartridge is taken out and remounted in this state, the posture of the cartridge is greatly changed, so that the toner inside the cartridge is vibrated, and the toner that adheres to the inner wall of the developing container can be moved. become.

JP 2003-215893 A JP-A-62-237477

  However, when the remaining toner is low and the user shakes the cartridge, the toner is often moved in the vicinity of the developing roller. However, depending on the handling, the longitudinal unevenness of the toner coat may remain. was there.

  Even when the longitudinal unevenness of the toner coat is eliminated, the toner charged state becomes unstable due to the mixture of the toner that has continued to receive the charging history and the toner that has not received the charging history on the surface of the developing roller. There was a possibility.

  When an image printing operation is performed in this state, density unevenness may occur in the longitudinal direction of the developing roller in either case described above.

  The present invention achieves an improvement in the chargeability of the toner carried on the developer carrier inside the development unit and the stabilization of the coating state in the process cartridge after the developer amount is reduced and detached, and more An object is to provide an image forming apparatus capable of obtaining a stable image.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an amount detecting unit that detects an amount of developer in a process cartridge having a developing unit, and the process cartridge is mounted on a main body of the image forming apparatus. The amount detecting means detects the amount of developer inside the process cartridge, and the process cartridge is detached after determining that the amount of developer inside the process cartridge has decreased based on the detection result detected by the amount detecting means. A controller that controls to change process conditions inside the image forming apparatus main body depending on whether the process cartridge is already used or is a separately used process cartridge that is mounted separately. And.

  According to the present invention, in the process cartridge after the developer amount is reduced and detached, improvement in the chargeability of the toner carried on the developer carrier inside the development unit and stabilization of the coat state are realized. A more stable image can be obtained.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is sectional drawing which shows the structure of a developing device. It is a flowchart which shows the control process of a controller. 10 is a flowchart showing a control process of a controller used in the image forming apparatus according to Comparative Example 1. FIG. 6 is a timing chart showing timings for driving a motor and applying a charging bias and a developing bias when a controller extends the pre-rotation time. FIG. 10 is a flowchart illustrating a control process of a controller provided in the image forming apparatus according to the second embodiment. 10 is a flowchart illustrating a control process of a controller included in an image forming apparatus according to Embodiment 3.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 according to Embodiment 1 of the present invention. The image forming apparatus 100 is an image forming apparatus using an electrophotographic image forming process. As shown in FIG. 1, the image forming apparatus 100 has an image forming apparatus main body (hereinafter, simply referred to as “apparatus main body”) 100A. Inside the apparatus main body 100A, an image forming unit 51 for forming an image is provided. Provided. The image forming unit 51 includes a photosensitive drum 1 that is an “image carrier”, a transfer roller 5 that is a “transfer device”, and the like.

  In this embodiment, the present invention is applied to a case where the cartridge is detached and the use is continued after the detection sensor detects the toner Out. Hereinafter, the operation of the image forming apparatus 100 will be described with reference to FIG. The photosensitive drum 1 is brought into contact with a charging roller 2 as a contact charging member, a charging bias is applied to uniformly charge the surface, and exposure is performed by an exposure device 3 (an apparatus that irradiates a laser or the like) as an exposure unit. As a result, an electrostatic image is formed on the surface. Thereafter, the photosensitive drum 1 is developed with the toner T (developer) by the developing device 4 to form a toner image (developer image) on the surface.

  On the other hand, the sheet S stored in the feeding cassette 20 is conveyed to the nip between the photosensitive drum 1 and the transfer roller 5, and the developer image is transferred by the transfer roller 5. Thereafter, the sheet S is conveyed and fixed to a fixing device 7 as fixing means, and an image is obtained and discharged to the tray 6. The toner T remaining on the surface of the photosensitive drum 1 is collected in the cleaner container 9 by the cleaning blade 8. In this embodiment, the developing device 4, the photosensitive drum 1, the charging roller 2, the cleaning blade 8, and the cleaner container 9 are configured to be detachable and replaceable from the apparatus main body 100 </ b> A as an integrated cartridge 10.

  In addition, a controller 50 that controls driving of the internal devices of the apparatus main body 100A is disposed inside the apparatus main body 100A. The controller 50 includes a storage unit 50a and a frequency detection unit 50b. The storage unit 50a and the number detection unit 50b will be described later. Further, the apparatus main body 100A is provided with a switch 21 for detecting whether or not the cartridge 10 is mounted.

  FIG. 2 is a cross-sectional view showing the configuration of the developing device 4. The developing device 4 includes a toner container 12 that is a “developing device body”. The toner container 12 contains toner T which is a one-component magnetic developer. An agitating member 13 is rotatably disposed inside the toner container 12 and plays a role of feeding the toner T to the developing unit. The sent toner T is taken into the developing sleeve 14 which is a “developer carrier”. Inside the developing sleeve 14, a magnet roller 15 as magnetic field generating means is inserted. When the cartridge 10 is mounted on the apparatus main body 100A, the magnet roller 15 is fixed, and the developing sleeve 14 is supported so as to be rotatable around the magnet roller 15 in a certain direction. The toner T on the surface of the developing sleeve 14 is conveyed by the magnetic force of the magnet roller 15 and the rotational force of the developing sleeve 14.

  The conveyed toner T is regulated to a certain amount by the blade 16 which is a developer carrying member, and further charged by friction between the blade 16 and the developing sleeve 14. The toner T that has been charged and regulated develops the electrostatic image formed on the photosensitive drum 1 by a developing bias (not shown) applied to the developing sleeve 14.

  On the inner wall surface of the toner container 12 is a “detection sensor” that is an “amount detection means” that detects the amount of toner T that is a “developer amount” inside the cartridge 10 that is a “process cartridge” having a developing unit. The electrode 17 is attached. The electrode detects the amount of toner T in the vicinity of the developing sleeve 14. When a developing bias is applied to the developing sleeve 14, the voltage induced in the electrode 17 is detected, and the toner amount in the vicinity of the developing sleeve 14 is detected by performing a calculation process. The detection by the electrode 17 utilizes the fact that the induced voltage varies depending on the amount of toner existing between the developing sleeve 14 and the electrode 17.

  And from this, the controller 50 performs the following control. That is, the controller 50 first controls the electrode 17 to detect the amount of toner T inside the cartridge 10 when the cartridge 10 is mounted on the apparatus main body 100A. When the controller 10 determines that the amount of toner T inside the cartridge 10 has decreased based on the detection result detected by the electrode 17, the controller 50 performs the following control. That is, the controller 50 controls the process conditions inside the apparatus main body 100A to be changed depending on whether the cartridge 10 is already used or is a separately used cartridge 10 that is mounted separately. The change of the process condition referred to here includes at least the extension of the pre-rotation time during which the photosensitive drum 1 disposed inside the apparatus main body 100A rotates before entering the image forming operation.

  Specifically, the controller 50 performs the following control based on the detection result detected by the electrode 17. That is, the controller 50 extends the pre-rotation time when the amount of toner T inside the cartridge 10 is smaller than a predetermined amount, and when the amount of toner T inside the cartridge 10 is larger than the predetermined amount. Do not extend the pre-rotation time.

  Here, a detection procedure for detection of attachment / detachment of the cartridge 10 will be described. When the cartridge 10 is mounted at a predetermined position on the apparatus main body 100A, the switch 21 (see FIG. 1) of the apparatus main body 100A is operated accordingly, and whether or not the cartridge 10 is mounted on the apparatus main body 100A is checked. Is detected.

  When the cartridge 10 is mounted on the apparatus main body 100A, the individual information of the cartridge 10 is read into the controller 50 (see FIG. 1) of the apparatus main body 100A, and the individual information is stored in the storage unit 50a of the controller 50. Is done. Then, when the cartridge 10 different from this is mounted after the used cartridge 10 is taken out, the individual information of the cartridge 10 mounted separately and the individual information of the used cartridge 10 are collated. . Then, it is detected whether an already used cartridge 10 is installed or a newly used cartridge 10 is installed.

  As described above, the cartridge 10 is detected to be attached / detached by detecting the presence / absence of mounting and collating individual information.

  FIG. 3 is a flowchart showing the control process of the controller 50. FIG. 3 is a flowchart when the cartridge 10 attached to the image forming apparatus 100 is detached only once after the state of “toner out” (a state where the residual toner is extremely low) is detected. Equivalent to. Here, the pre-rotation time before image formation is extended after the cartridge 10 is removed. FIG. 3 partially includes user operations (S3, S4).

  Also, this example was compared with the following comparative example 1. The configuration of Comparative Example 1 is as follows.

  In Comparative Example 1, after the cartridge 10 is attached and detached, the pre-rotation time is not always extended, and the same setting as before the cartridge 10 is used is used. FIG. 4 is a flowchart illustrating a control process of a controller used in the image forming apparatus according to the first comparative example. In both Example 1 and Comparative Example 1, the cartridge 10 was attached and detached when the toner remaining amount in the cartridge 10 detected “toner Out”.

  First, as shown in FIG. 3, in the first embodiment, the electrode 17 detects “toner Out” (step 1, hereinafter, “step” is simply referred to as “S”; S1). In the apparatus main body 100A, the controller 50 reads the unique information of the cartridge 10 and stores it in the storage unit 50a (memory) that is a part of the controller 50 together with the toner Out information (S2). The user removes the cartridge 10 from the apparatus main body 100A (S3). The user attaches the cartridge 10 to the apparatus main body 100A (S4). Memory information of the loaded cartridge 10 is read (S5). Whether or not the cartridge 10 attached to the apparatus main body 100A is the cartridge 10 previously taken out by the user (that is, whether the cartridge 10 was taken out last time or separately attached) is recorded in the storage unit 50a. Based on the above, the controller 50 compares them (S6).

  As a result of the comparison in S6, if the cartridge 10 was taken out last time, it is determined that “toner Out / cartridge remount” (S7). If the result of the comparison in S6 is other than S7, it is determined that it is a separate (other) cartridge 10 that is not the previously removed cartridge 10 (S8). After the determination in S8, the remaining amount of toner is detected, and it is determined whether or not the toner is out (S9).

  As a result of the determination in S9, if it is determined that the toner is out, it is determined that “toner out / cartridge remounting”, and the toner out information is written in the storage unit of the controller 50 together with the unique information of the cartridge 10 (S10). . As a result of the determination in S9, when it is determined that the toner is not toner Out, it is determined that a separate cartridge 10 is mounted (S11).

  If it is determined that “toner out / cartridge remount” as in S10, the mode is changed to a mode in which the pre-rotation time before image formation is extended (S12). Then, the standby state is entered (S13). If it is determined that the cartridge 10 is not a toner out as in S11, it directly shifts to the standby state (S13).

  If it is determined as “toner out / cartridge remount” as in S7, the mode is changed to a mode for extending the pre-rotation time before image formation (S12). Then, the standby state is entered (S13).

  In S3 and S4 described above, whether the cartridge 10 is attached to the apparatus main body 100A is detected by the operation of the switch 21 of the apparatus main body 100A described above. Further, by comparing the individual information of the cartridge 10 recorded in S2 with the individual information of the cartridge 10 captured in S5, it is determined whether the cartridge 10 is remounted or separately mounted (S6, S7, S8) is determined.

  In Comparative Example 1, in any case, the pre-rotation time remains as it is, and S21 to S33 of Comparative Example 1 are the same as S1 to S11 and S13 of Example 1, and description of Example 1 The duplicate description is omitted. Further, the control of Comparative Example 1 is different from that of Example 1 in that Comparative Example 1 does not have the step S12 of Example 1.

  FIG. 5A is a timing chart showing the driving timing of the photosensitive drum 1 motor and the timing of applying the charging bias and the developing bias when the controller 50 extends the pre-rotation time. FIG. 5B is a timing chart showing the driving timing of the photosensitive drum 1 motor and the timing of applying the charging bias and the developing bias when the controller 50 does not extend the pre-rotation time. 5A shows that the pre-rotation time before the image forming operation is set longer than that in FIG. 5B.

  Next, actual effects confirmed in Example 1 and Comparative Example 1 will be described. The conditions are as follows. (A) The cartridge 10 in which the toner Out (remaining amount 2%) is detected is used. (I) The cartridge 10 is detached and attached in that state. (Iii) One image is printed intermittently (one sheet) (E) Pre-rotation time extension shall be 3 seconds longer.

  First, Table 1 shows a result of comparison of how many sheets can be printed after the toner Out is detected and the cartridge 10 is shaken. In Table 1, the ◯ Δ level is a level at which slight shading unevenness can be recognized.

  In Example 1, white spots occurred on the 24th sheet after desorption. On the other hand, in Comparative Example 1, slight unevenness of the image appeared in the first image after mounting, and white spots occurred on the 20th image.

  In Comparative Example 1, the reason why the unevenness of the image appears after the remounting is that the toner coat unevenness occurs after the 15th printing due to the occurrence of white spots, and the first printing after the remounting of the cartridge 10 is performed. This is because the uneven coating could not be solved sufficiently. However, since an image with no problem is obtained by printing on the second sheet, it can be seen from this that the effect of this embodiment can be easily solved by extending the rotation time. Further, in Comparative Example 1, the occurrence of white spots again is faster than in the present example. Compared to this example, it can be seen that it is difficult to eliminate uneven coating when the amount of toner decreases.

  On the other hand, in the present embodiment, by performing pre-rotation extension, it is easier to eliminate coating unevenness and coating charging unevenness, and a stable coating state can be realized in a longer period of time, which is superior to Comparative Example 1. It can be said that.

  In the embodiment, the process condition is changed by extending the pre-rotation time during which the photosensitive drum 1 disposed inside the apparatus main body 100A rotates at least before entering the image forming operation. It is not a thing. That is, it is conceivable to change the conditions to be advantageous for development by reducing the image forming speed (process speed), adjusting the developing bias, or the like. These may be combined with the extension of pre-rotation.

  As in this embodiment, the cartridge 10 may not be attached / removed immediately after the detection of the toner Out, but may continue to be used for a while after the detection of the Out and a white spot occurs and is reattached. However, in this case as well, by extending the pre-rotation after the cartridge 10 is removed, the remaining toner can be coated more stably, so that the same effect as in this embodiment can be exhibited.

  In the present embodiment, the case where the removal / desorption is detected after detecting the toner Out in a state where the residual toner is extremely small is shown. However, the toner Low (the state where the amount of residual toner is larger than the toner Out but close to Out) is detected. If detected, desorption may be detected to change the process conditions.

  In the present embodiment, the result of storing the toner remaining amount detecting means of the cartridge 10 is stored in the controller 50 of the apparatus main body 100A together with the individual information. However, a storage unit is provided inside the cartridge 10 and connected to the controller 50 of the apparatus main body 100A, the remaining amount detection result is stored in the storage unit of the cartridge 10, and the attachment / detachment is detected by reading the information and the individual information at the time of remounting. However, similar control can be performed.

  In this embodiment, the toner remaining amount detecting means uses a remaining amount detecting method for directly detecting the toner amount in the vicinity of the developing sleeve 14. However, even if a method of counting the amount of consumed toner by processing image data to be printed and counting pixels of the image printing portion is applicable without particular problem.

  FIG. 6 is a flowchart illustrating a control process of the controller 50 provided in the image forming apparatus 100 according to the second embodiment. Of the configuration of the image forming apparatus 100 according to the second embodiment, the same configuration, control, and effect as those of the image forming apparatus 100 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate. Among the control steps of the controller 50 of the second embodiment, the following points are different from the control steps of the controller 50 of the first embodiment. That is, in the second embodiment, the controller 50 sets the extension time of the pre-rotation time to be longer as the decrease rate of the amount of toner T inside the cartridge 10 is larger based on the detection result detected by the electrode 17. It is characteristic. Details will be described below.

  In the first embodiment, the process condition is changed depending on whether or not the toner Out is detected. On the other hand, in the second embodiment, the case where the process condition is changed when the toner remaining amount of the cartridge 10 is the toner low and the toner out is shown. As described above, when the amount of toner is relatively large, charging uniformity is more problematic than unevenness of the toner coating itself, and when the amount of toner is small, the stability of the coating itself is problematic. That is, if the amount of remaining toner T is relatively large, charging may be performed, so that the pre-rotation time is short. However, if the amount of remaining toner T is relatively small, the coat itself needs to be stabilized. It is necessary to lengthen the pre-rotation time. In this embodiment, the value is set as shown in Table 2 depending on the value of the remaining amount detection result when desorption is performed.

  The steps up to and including the reading of information by removing the cartridge 10 in FIG. 6 (S41 to S45) are the same as those in FIG. 3 (S1 to S5) of the first embodiment. However, the following points are different. That is, when it is determined that the same cartridge 10 as the previous one is attached when the cartridge 10 is attached, the remaining amount information of the toner of the cartridge 10 stored last time is read (S42, S47), and the remaining amount information The pre-rotation time is changed according to (S48 to S52). When it is determined that a separate cartridge 10 is mounted when the cartridge 10 is mounted, the remaining amount of toner is detected to obtain remaining toner information, and the pre-rotation time is changed according to the remaining amount information. (S53 to S58). The steps after remounting the cartridge 10 will be described below.

  As a result of determining whether or not it is the previous cartridge 10 (S46), if it is determined that the previously removed cartridge 10 is remounted (S47), it is determined whether or not the remaining amount of toner is 3% or less. (S48).

  As a result of the determination in S48, if the remaining amount of toner is 3% or less, a mode for extending the pre-rotation time by 3 seconds is entered (S49), and a standby mode is entered (S50). If the result of determination in S48 is that the remaining amount of toner is not 3% or less, it is determined whether or not the remaining amount of toner is 10% or less (S51). If the result of determination in S51 is YES, that is, if it is determined that the remaining amount of toner is greater than 3% and less than or equal to 10%, the pre-rotation time is extended by 1.5 seconds (S52), and the standby mode is entered ( S50). When the remaining amount of toner is larger than 10%, the standby mode is entered without entering the mode for extending the pre-rotation time (S50).

  If a new cartridge 10 is mounted as a result of the determination in S46 (S53), the remaining amount of toner is detected again because the controller 50 originally has only information on the previous cartridge 10 (S54). Then, it is determined whether the remaining amount of toner is 3% or less (S55).

  As a result of the determination in S55, if the remaining amount of toner is 3% or less, a mode for extending the pre-rotation time by 3 seconds is entered (S56), and a standby mode is entered (S50). If the result of the determination in S55 is that the remaining amount of toner is not 3% or less, it is determined whether or not the remaining amount of toner is 10% or less (S57). If the result of determination in S57 is YES, that is, if it is determined that the toner remaining amount is greater than 3% and less than or equal to 10%, the pre-rotation time is extended by 1.5 seconds (S58), and the standby mode is entered (S58). S50). If the result of determination in S57 is NO, that is, if the remaining amount of toner is greater than 10%, the standby mode is entered without entering the mode for extending the pre-rotation time (S50).

  Here, the effect of a present Example is demonstrated using the comparative examples 2-4 which perform pre rotation with the following specifications. The specifications of Comparative Examples 2 to 4 are shown in Table 3.

  In order to demonstrate the effect, the cartridge 10 is removed when the remaining amount of toner T is 7% and when the cartridge 10 is removed when the remaining amount of toner T is 2%. Compare rotation times. Also, is uneven density occurring? , How many white spots will occur after removal? Compare Table 4 shows the comparison results.

Here, Δ is a conspicuous level with a clearer shade difference than ○ Δ.

  From Table 4, it can be seen that when the remaining amount of toner T is 7%, it is not necessary to extend 3 seconds and there is no problem with 1.5 seconds. However, although it is very slight without extension, the first sheet has unevenness in density, and it can be seen that there is an extended effect. Of course, since the time was short and the same effect on the image was obtained, it was shown that the present example and comparative examples 2 to 4 have a sufficient effect.

  On the other hand, when the toner T is desorbed with a remaining amount of 2%, △ level shading unevenness occurs even with 1.5 second extension other than without pre-rotation, but there is no problem with 3 second extension. It was able to be set as the level, and it was shown that it is the composition excellent compared with comparative examples 2-4.

  Judging from the above, it can be seen that the necessary number of pre-rotations can be extended with the configuration of the present embodiment, so that the number of printed sheets can be extended without any problem on the image.

  FIG. 7 is a flowchart illustrating a control process of the controller 50 included in the image forming apparatus 100 according to the third embodiment. Of the configuration of the image forming apparatus 100 according to the third embodiment, the same configurations, controls, and effects as those of the image forming apparatus 100 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate. Among the control steps of the controller 50 of the third embodiment, the following points are different from the control steps of the controller 50 of the first or second embodiment. In other words, the controller 50 includes a number detection unit 50b (see FIG. 1) that detects the number of times the cartridge 10 is attached and detached, and the more the number of times the cartridge 10 is attached and detached based on the detection result detected by the number detection unit 50b. In addition, the extension time of the pre-rotation time is set longer. Details will be described below.

  In the first embodiment and the second embodiment, the case where it is determined whether or not to extend the pre-rotation time by one detachment of the cartridge 10 is shown. On the other hand, in this embodiment, a case where the pre-rotation time extension condition is adjusted according to the number of times the cartridge 10 is detached from the apparatus main body 100A after detecting the toner Out is shown. Note that such a situation as described in this example may actually occur sufficiently when considering jam processing when the amount of toner is low.

  The steps up to and including the reading of information by removing the cartridge 10 in FIG. 7 (S61 to S65) are the same as those in FIG. 3 (S1 to S5) of the first embodiment. However, the following points are different. In other words, when the pre-rotation time has already been extended at the time of mounting, the point of further extension is different. The steps after remounting the cartridge 10 will be described.

  As a result of determining whether or not it is the previous cartridge 10 (S66), if it is determined that the previously removed cartridge 10 has been remounted (S67), it is determined whether or not the pre-rotation time extension has already been turned on. (S68).

  As a result of the determination in S68, if the pre-rotation time extension is already On, the pre-rotation time is extended from 3 seconds to 5 seconds (S69), and the standby mode is entered (S70). If the result of determination in S68 is that the pre-rotation time extension has not yet been turned on, a mode for extending the pre-rotation time by 3 seconds is entered (S71), and a standby mode is entered (S70).

  If another cartridge 10 is mounted as a result of the determination in S66 (S72), the remaining amount of toner is detected again because the controller 50 originally has only information on the previous cartridge 10 (S73). Then, it is determined whether or not the toner is out (S74).

  As a result of the determination in S74, if it is determined that the toner is Out, the remaining amount detection result is written in the memory (S75), the pre-rotation time is extended by 3 seconds (S76), and the standby mode is entered (S70). . As a result of the determination in S74, if it is determined that the toner is not toner out (S77), the standby mode is directly entered (S76).

  Here, the effect of the present embodiment will be described using Comparative Example 5 in which the pre-rotation time is only extended by 3 seconds even after the second desorption.

  The specifications of this example and comparative example 5 were as follows. That is, when the toner Out (remaining amount is 2%) is detected, the cartridge 10 is immediately detached, 10 images are printed, the cartridge 10 is detached again, and printing is continued.

  Table 5 shows how the pre-rotation time is extended by desorption in this example and comparative example 5.

  Table 6 shows how many sheets have been printed since the first removal.

In this embodiment, the number of printable sheets is larger, and it can be seen that there is an effect of extending the pre-rotation time after the second desorption. However, if it is further extended, the throughput is simply slowed, so it is not as good as increasing the time. From the above, it was shown that this example is also effective.

  In this example, whether or not the cartridge 10 is attached / detached is determined based on whether the same cartridge 10 is attached and whether the pre-rotation time has been extended, but the number of times of attachment may be stored when the cartridge 10 is attached.

  Further, as described above, since desorption greatly affects density unevenness when the remaining amount of toner decreases, it is sufficient to record desorption after the remaining amount of toner has decreased to some extent. It is. In other words, when the remaining amount of toner is equal to or greater than a predetermined value, it is not necessary to perform desorption detection.

  According to the configuration of Embodiment 1 or 2, in the cartridge 10 after the amount of the toner T is reduced and detached, the chargeability of the toner carried on the developing sleeve 14 in the developing unit is improved and the coating state is increased. Stabilization is realized and a more stable image can be obtained. Further, the toner T remaining in the cartridge 10 contributes to image formation more effectively.

10 Cartridge (process cartridge)
17 Electrode (quantity detection means)
50 controller 100 image forming apparatus 100A apparatus main body (image forming apparatus main body)
T toner (developer amount)

Claims (5)

An amount detecting means for detecting the amount of developer inside the process cartridge having the developing unit;
When the process cartridge is mounted on the main body of the image forming apparatus, the amount detection unit detects the amount of developer inside the process cartridge, and the development inside the process cartridge is performed based on the detection result detected by the amount detection unit. When the process cartridge is detached after it is determined that the amount of the agent has decreased, the image forming apparatus depends on whether the process cartridge is already used or is a separately used process cartridge. A controller that controls to change the process conditions inside the body,
An image forming apparatus comprising:   The change in the process condition includes an extension of a pre-rotation time during which an image carrier disposed inside the image forming apparatus main body rotates at least before entering an image forming operation. Image forming apparatus.   Based on the detection result detected by the amount detection means, the controller extends the pre-rotation time when the amount of developer inside the process cartridge is less than a predetermined amount, and develops the inside of the process cartridge. The image forming apparatus according to claim 2, wherein the pre-rotation time is not extended when the amount of the agent is larger than a predetermined amount.   The controller sets a pre-rotation time extension time to be longer as a decrease rate of the developer amount inside the process cartridge is larger based on a detection result detected by the amount detection means. Item 3. The image forming apparatus according to Item 2.   The controller includes a number detection unit that detects the number of times the process cartridge is attached / detached, and based on the detection result detected by the number detection unit, the more the number of times the process cartridge is attached / detached, the greater the pre-rotation time. The image forming apparatus according to claim 2, wherein the extension time is set long.